#include <bits/stdc++.h>
#define X first
#define Y second
using namespace std;
ifstream fin("lupu.in");
ofstream fout("lupu.out");
long long n,x,l,a,b,maxim,i;
pair<long long, long long> v[100010];
multiset<long long> s;
multiset<long long>::iterator it;
int main(){
    fin>>n>>x>>l;
    for(i=1;i<=n;i++){
        fin>>a>>b;
        v[i].X=(x-a)/l;
        v[i].Y=b;
    }
    sort(v+1,v+n+1);
    for(i=v[n].X;i>=0;i--){
        while(n>=1&&v[n].X==i){
            s.insert(v[n].Y);
            n--;
        }
        if(!s.empty()){
            it=s.end();
            it--;
            maxim+=*it;
            s.erase(*it);
        }
    }
    fout<<maxim;
    return 0;
}